This invention relates to silicone compounds which are useful as foam control agents in foaming systems. More particularly this invention relates to arylalkyl modified silicone polyethers and to their use as foam control agents in hydrocarbon liquids.
Current fuels exhibit foaming during transfer operations, such as filling a vehicle's fuel tank at a filling station. In the processing, transportation and storage of hydrocarbon liquids, it is frequently observed that foaming occurs as the liquid is passed from one vessel to another. For example, as liquid hydrocarbon fuel is passed quickly into a storage tank a foam may develop at the surface of the fuel and, in many cases, the extent of foaming is sufficiently significant and persistent to require a reduction in the rate of passage of the liquid fuel into the vessel. It is highly desirable to provide means for controlling foaming so as to permit high rates of passage.
There are a number of patents which disclose compositions which reduce or eliminate foam in hydrocarbon liquids. For example Moorehouse et al. in U.S. Pat. No. 3,233,986 discloses siloxane polyoxyalkylene block copolymers having groups represented by the formula R.sub.b SiO.sub.4-b/2 wherein R is a monovalent hydrocarbon group or a divalent hydrocarbon group and b has a value from 1 to 3 inclusive, and groups having the formula ##EQU1## or having the formula ##EQU2## wherein G'" is a member selected from the group consisting of the hydrogen atom and the monovalent hydrocarbon groups, G" is an alkylene radical containing at least two carbon atoms, G' is a divalent hydrocarbon radical, G is a monovalent hydrocarbon radical, n has a value of at least two and c has a value from 0 to 2 inclusive. Moorehouse et al. discloses that these siloxane polyoxyalkylene block copolymers are useful in reducing the tendency of various hydrocarbon liquids such as kerosene, gasoline, or diesel fuel to foam.
Adams et al in U.S. Pat. No. 4,690,668 discloses a method of controlling foaming of liquid hydrocarbon fuels such as diesel fuel and jet fuel by inclusion therein of certain siloxane polyoxyalkylene copolymers as antifoam agents. Adams et al. further discloses that the copolymers have an average molecular formula such that the oxyalkylene groups of the copolymer provide from about 25% to about 65% by weight of the copolymer.
Callaghan et al. in U.S. Pat. No. 4,711,714 discloses water-insoluble siloxane polyoxyalkylene graft copolymers which are effective antifoam agents for reducing foaming in crude oil/gas separators. Callaghan et al. discloses that the copolymers are particularly useful in breaking microgas dispersions and foams resulting from crude oils with a high gas to oil ratio.
German Patent Specification No. 4032006 discloses a process for defoaming and/or degassing organic systems by adding to the organic system an antifoaming agent containing an organopolysiloxane having siloxane units of the formula ##EQU3## where R is a monovalent hydrocarbon radical having 1 to 182 carbon atoms per radical and A denotes a radical the general formula ##STR2## where R.sup.1 denotes a radical of the formula --CR.sup.3 H--with R.sup.3 being a hydrogen atom or a monovalent organic radical, R.sup.2 denotes a radical of the formula --CR.sup.4 H--CH.sub.2 --or --CH.sub.2 CH.sub.2 CH.sub.2 --where R.sup.4 denotes a hydrogen atom or a monovalent organic radical, v and w at any given time are 0 or a whole number and the sum of v+w on average is 0 to 16, x and y at any given time are 0 or 1 and the sum of x+y is 1 or 2, a is 1-3, b is 0-2, and c is 1 or 2 and the sum of b+c is not greater than 3. It is further disclosed that these organopolysiloxanes are especially useful as foam suppressants or degassing agents in diesel oils, jet fuels, and crude oils.
German Patent Specification No. 4325359 discloses a process for defoaming and/or degassing organic systems by adding to the organic system an antifoaming agent containing an organopolysiloxane having siloxane units of the formula ##EQU4## where R is an SiC bound monovalent hydrocarbon radical having 1 to 18 carbon atoms per radical and A denotes a radical the general formula ##STR3## where R.sup.1 denotes a divalent hydrocarbon radical having 1 to 6 carbon atoms, R.sup.2 denotes a divalent hydrocarbon radical having 2 to 4 carbon atoms, R.sup.3 denotes a divalent hydrocarbon radical having 2 to 6 carbon atoms, c, x, and y are 0 or 1, v, w, s, and t are 0 or an integer such that v+w is 0 to 16, s+t is 1-20, x+y is 1 or 2, a is 1-3, b is 0-2, and a+b is 3 or less. It is further disclosed that these organopolysiloxanes are especially useful as foam suppressants or degassing agents in diesel oils, jet fuels, and crude oils.
German Patent Specification No. 4343235 discloses organofunctional polysiloxanes having a mixture of radicals, the first radical being selected from (a) the radical ##STR4## wherein R.sup.3 is hydrogen or an alkyl radical, c is a number from 1 to 20, d is a number from 0 to 50, and e is a number from 0 to 50, (b) the radical --(CH.sub.2).sub.f OR.sup.4 where R.sup.4 is hydrogen or a monovalent organic radical and f is a number from 3 to 20, and (c) the radical (CH.sup.2).sub.g (OC.sub.2 H.sub.4).sub.h (OC.sub.3 H.sub.6).sub.i OR.sup.5 where R.sup.5 is hydrogen or a monovalent organic radical, g is a number from 3 to 6, h is a number from 1 to 50, and i is a number from 0 to 20, and the second radical being selected from (d) the radical ##STR5## where R.sup.6 is a hydrocarbon radical or an alkyl radical, R.sup.7 is an alkyl radical, an acyl radical, or a trialkylsilyl radical, k is a number from 1 to 20, m is a number 0 to 50, and n is a number from 0 to 50, (e) the radical --(CH.sub.2).sub.o CH.sub.3 where o is a number from 5 to 30, or (f) the radical --(CH.sub.2).sub.g (OC.sub.2 H.sub.4).sub.h (OC.sub.3 H.sub.6).sub.i OR.sup.5 where R.sup.5 is hydrogen or a monovalent organic radical, g is a number from 3 to 6, h is a number from 0 to 35, and i is a number from 1 to 50. These organopolysiloxanes are disclosed as being useful for defoaming diesel fuel in amounts of 0.5 to 50 ppm with respect to diesel fuel.
Fey et al. in U.S. Pat. No. 5,397,367 discloses organosilicon materials that are density matched to the hydrocarbon medium and also act as foam control agents in hydrocarbon fuel, specifically as described therein for diesel fuel. These new foam control agents are disclosed as being crosslinked organopolysiloxane-polyoxyalkylene polymers. Fey et al. further discloses that these polymers have the characteristic of being slightly soluble or insoluble in water and hydrocarbon fuels.
The use of conventional silicone polyethers, which because of their higher density relative to hydrocarbon fuel can settle out of the fuel over time, potentially renders them less effective without periodic agitation to re-disperse them. Conventional silicone polyethers also can suffer from the fact that they tend to be more soluble or dispersible in water, a constant component of hydrocarbon fuels. In storage tanks, water tends to coalesce, forming a layer at the bottom of the tank. As the silicone polyether settles due to gravity and its insolubility in the hydrocarbon, eventual contact with the water layer can result in its being absorbed into or complexed as a result of its surfactancy with that phase, thus irreversibly removing it from the fuel entirely.
A number of proposals have been made for controlling foaming of various grades of hydrocarbon liquids by use of additives: for example, silicone products as described above. However, the reduction of foaming in diesel fuels by the use of technically acceptable silicone additives has not been completely resolved prior to this invention.